There's been a murder!

Phytomyza ilicis, the holly leaf miner, is a fly that lays its eggs in holly leaves. In the spring, when the leaves are still soft, a female fly lays her  eggs in a holly leaf, near to the midrib using a hypodermic needle-like ovipositor. The larvae or maggots soon emerge from the eggs and tunnel their way along the midrib, emerging some time later into the interior of the blade of the leaf.  Here they feed on the photosynthetic tissues of the leaf, creating a leaf mine.
The fully grown larva pupates in the leaf and eventually an adult fly emerges from the leaf mine via a very small hole. However, many larvae and pupae are predated by small birds before they reach maturity. The miner in the photograph, met such a fate, as evidenced by the brown beak-shaped tear in the leaf.